I've heard people say that SACD ought to fail in transient reproduction, (because it can only encode a rise and fall relative to the last time step) so I did some calculations:

'Sampling rate' of SACD = 2.8MHz = 64x 44.1kHz

For encoding tones up to 44.1kHz at full scale, it has to reach full-scale from 0 in 64 steps, that is, at any given time there can only be 64 possible positions for the waveform.

This gives it 6 bits resolution to CD's 16 bits??

OK, suppose you only need to encode up to 22.05kHz at full scale, the number of possible positions increases from 64 to 128--7 bits resolution, big improvement

I doubt this is how DSD actually works, but this article http://www.iar-80.com/page40.html (I linked to page 40, but it seems page 1-39 may be going on and on about the sonic flaws of DSD as well) seems to take this view seriously and goes on to talk about how you try to recover musical information from the 6 bit stream.

There haven been a number of publications in the past 10 years about the capability of the Human ear to 'hear' sound > 20 KHz ( dont ask me for any links, i dont have any avaialble )

I only know of one study done by japanese researchers, where they "measured" different brain waves when the test subject was exposed to high ultrasonic levels. However, the subject didnt hear anything, and the different brain waves were present even after the utrasonic sound ceased. No one was able to repeat this experiment, iirc.

If you know of another REAL study about this, it would be interesting to know about it. But not of the type "I've heard" or "I've read somewhere" myths.

QUOTE

did tests with my own ears, almost 5 years ago :- I was not able to 'hear' sine tones > 16.5 KHz ( maybe even lower now )but- in a blind ABX test i could easily detect a low pass filter of 4th order ( 24 db/octave , linkwitz ) with a -3 dB at 20 KHz on a high quality Stereo chain, with normal music ( hitrate : > 85 % ) .Why ?

Maybe your filter with -3 dB at 20 KHz was something like -1 dB at 13 KHz, I don't know. This would be quite audible with harmonic-type musical signals.

The thing is that I can hear up to 18 - 18.5 KHz with sine signals, but can't differentiate an impulsive clip such as castanets attack brickwall-filter lowpassed at 15 KHz from non-lowpassed. Even have some difficulties with a 12 KHz lowpass. Just try at http://www.pcabx.com/technical/low_pass/index.htm. Just try to ABX any of the 18 KHz lowpassed clips, and tell me if you are able to hear them sound different. Go down into the lowpass until you can hear the difference.

This is because with this more complex real world signals, masking comes into effect, and the lower high frequencies easily mask the higher high frequencies. This doesn't happen with pure tones (sines).

About localization, what happens is that ear is very sensitive to interaural delays, but if you lowpass both channels the same way, the interaural delays remain the same. Even when ear is so sensitive to interaural delays, this doesn't has much to do with the upper frequency limit of hearing.